Method and apparatus for continuous casting

ABSTRACT

A tundish receiving molten metal and a cooled, closed-end mold are moved relatively apart so that the mold forms a solidified shell of a casting such as a billet, for example, molten metal flowing through the solidified shell to the mold. At least a portion of the closed end or plug of the mold is heated at least during a preheating period to limit or eliminate the formation of a solidifying metal membrane on at least a portion of the closed end. A lubricant and/or a seal may be introduced between an axial wall structure of the mold and the mold plug, and at least a portion of the mold is oscillated relatively to the shell in the mold during casting. The plug in one position thereof may occupy a forward or starting position in the end portion of axial wall structure nearest the tundish. In addition to preheating the tundish before receiving molten metal for flow therethrough, at least a portion of the plug is heated in its forward position during the preheating operation. The axial wall structure may be heated in the preheating operation to remove any condensation from the interior thereof. Thereafter, the near end face of the axial wall structure is abutted against a flange of the tundish prior to the flow of metal through the tundish to the mold. This retraction of the plug produces, with the axial wall structure coacting with the plug, a mold having a variable effective mold cavity.

United States Paten Watts 1 June 4, 1974 METHOD AND APPARATUS FOR CONTINUQUS CASTING 75 Inventor: Leonard Watts, Cedarhurst. NY.

[73] Assignee: Technicon Instruments Corporation,

Tarrytown, NY.

[22] Filed: July 5, 1972 [21] Appl. No.: 268,977

Related U.S. Application Data [63] Continuation-impart of Ser. Nos. 143,055, May 13, 1971, Pat. No. 3,680,624, and Ser. No. 171,283.

Aug. 12, 1971, abandoned.

3/1945 Italy 164/82 Primary Examiner-R. Spencer Annear Attorney, Agent, or Firm-S. P. Tedesco; S. E. Rockwell [571 ABSTRACT A tundish receiving molten metal and a cooled. closed-end mold are moved relatively apart so that the mold forms a solidified shell of a casting such as a billet, for example, molten metal flowing through the solidified shell to the mold. At least a portion of the closed end or plug of the mold is heated at least during a preheating period to limit or eliminate the formation of a solidifying metal membrane on at least a portion of the closed end. A lubricant and/or a seal may be introduced between an axial wall structure of the mold and the mold plug, and at least a portion of the mold is oscillated relatively to the shell in the mold during casting. The plug in one position thereof may occupy a forward or starting position in the end por tion of axial wall structure nearest the tundish. In addition to preheating the tundish before receiving molten metal for flow therethrough, at least a portion of the plug is heated in its forward position during the preheating operation. The axial wall structure may be heated in the preheating operation to remove any condensation from the interior thereof. Thereafter, the near end face of the axial wall structure is abutted against a flange of the tundish prior to the flow of metal through the tundish to the mold. This retraction of the-plug produces, with the axial wall structure-c0- acting with the plug, a mold having a variable effective mold cavity.

41 Claims; 13 Drawing Figures PATENTEDJUM 4 W SHiEISUf? PATENTEDJun 41914 sum 7 or 7 Q at Nmm METHOD AND APPARATUS FOR CONTINUOUS CASTING This application is a continuation-in-part of co- BACKGROUND OF THE INVENTION 1. Field of Invention This invention relates to apparatus for the continuous casting of metal utilizing a cooled, closed-end mold.

2. Prior Art There is illustrated and described in my U.S. Pat. No. 3,517,725 issued June 30, 1970, a technique of continuous casting utilizing a cooled closed-end mold relatively separated along a path from a tundish to form a solidified billet shell. There is described in that patent the possible formation of a membrane on at least a portion of the cooled end wall of the mold by metal solidifying thereagainst. This membrane may be ruptured or the formation thereof may be prevented by generating heat within the mold cavity but this prior art technique is disadvantageous. It has been found desirable to improve the technique and apparatus for eliminating or at least limiting the formation of such membrane in the casting process as described above.

Furthermore, in carrying out the casting technique illustrated and described in the last-mentioned patent some difficulty may be experienced in the release of the billet by the mold during casting because of problems encountered in injecting a lubricant between the billet being formed and the axial wall structure of the mold. This sticking or friction of the mold with the solidifying billet shell may create surface irregularities in the billet. While reference has been made to a billet, it is to be understood that the aforementioned casting problems are also believed to exist in the casting of other objectsdiffering widely in cross-sectional shapes and including articles having a letter I cross section, and of casting composite metal billets as described in my U.S. Pat. No. 3,625,277 issued Dec. 7, 1971, and casting of metal tubing such as illustrated and described in my US. patent application, Ser. No. 143,055, filed May 13, 1971, now U.S. Pat. No. 3,680,624 issued Aug. 1, 1972.

It has been found that preheating of the tundish alone as in the prior art is not sufficient. As far as is known, the prior art does not include the technique or apparatus for preheating the mold or portion thereof which preheating has been found desirable. In addition, it was found that improvements could be made in prior art starting bars. It has also been found desirable to improve the prior art cooperation of the tundish with the mold. Still another drawback to the known prior art constructions is that in the type casting apparatus described above, no plug has been provided to vary the effective capacity of the mold, which plug in one position thereof effects the aforementioned closed end of the mold. Such a variation is especially useful in preheating a certain portion of the mold for example, and in the start-up operation of casting metal.

SUMMARY OF THE INVENTION.

One Object of the invention is to provide an improved cooled, closed-end mold for use in the continuous casting of metals. A further Object is to provide an improved method and' apparatus for casting metal in which a tundish receiving molten metal and a closedend mold are moved relatively apart so that the mold forms a solidified shell of a casting such as a billet, for example, and wherein molten metal flows through the solidified shell to the mold from the tundish during the elongation of the billet. The closed end of the mold is heated in an improved manner to reduce or eliminate the formation of a metal membrane on the closed end during the casting. The heating of the mold end or plug permits a substantially constant flow of molten metal into the mold.

To avoid sticking of the mold to the shell with consequent detrimental effects, a lubricant may be introduced between at least a portion of the moldand the cooled axial wall of the mold, and the cooled axial wall structure of the mold may be oscillated relatively to the closed end or plug of the mold. This effectively tends to reduce friction or sticking of the mold to the casting and improves the surface characteristics of the billet. Still another object is to provide for the escape of excessive pressure, such as from gas or a fluid lubricant, from the mold during casting, which pressure is relieved in the area between the axial wall structure of the mold and the closed mold end or plug in one form of the invention. Another object is to provide casting apparatus providing any selected one of alarge variety of cross-sectional shapes in elongated articles, including articles having a letter I cross section by way of example only.

Furthermore the invention contemplates the preheating of the mold or a portion thereof, in addition to the preheating of the tundish. In connection with the aforementioned preheating but not limited thereto, it is an object to provide a mold having an axial wall structure coacting with what may be termed a closed end of the mold, which may take the form of a plug, which plug is movable axially within the axial wall structure to vary the effective mold cavity. This plug serves, in one oper-' ative position thereof within the aforementioned axial wall structure, as a closed end of the mold within the rear end portion of the axial wall structure. The plug may be movable to a forward position, so far forward as to protrude from the front end portion of the axial mold structure to be preheated at least in part. Aside from the preheating aspect of the plug previously described, the variable mold cavity is useful at the commencement of a casting operation, for example, Still another object is to provide in at least one form of the invention an improved plug design having effective provision to inhibitmolten metal entering the mold cavity from also entering a gap region between the plug and the internal surface of the axial wall structure of the mold. Also in at least some applications it is desirable to provide a member coacting with the plug and the last-mentioned surface of the axial wall' structure, which member may be rigid, which serves not only as a seal but also a lubricating function to reduce friction between the last-mentioned surface and the plug.

Yet another object of the invention is to provide in such casting apparatus improved cooperation of the metal-receiving mold end with the tundish and the de- 3 sign of the tundish nozzle or exit port. In addition, the invention contemplates improvements in starting bar constructions. r

BRIEF DESCRIPTION OF THE DRAWINGS I diagrammatically the pressure lubrication system and pressure-relief feature;

FIG. 4 is a somewhat diagrammatic side elevational view of a further modification of the invention;

FIG. 5 is a view similar to FIG. 4 showing parts of the apparatus indifferent positions; FIG. 6 is a view similar to FIG. 5 showing parts of the apparatus in different'positions;

- FIG. 7 is a view similar, to FIG. 6fshowing parts of the,

apparatus in different positions;

FIG. 8 is an enlarged fragmentary'view partially in section of a portion of the apparatus in: the condition ofFlG.4;

FIG. 9 is a view similar to FIG. 8 showing the apparatus in the condition of FIG. 5', e

' FIG. 10 is a view similar to FIG; 8 further illustrating a portion of the-apparatus illustrated in FIGS. 4-7; v

I FIG. 11 is an enlarged sectional view taken on line llll of FIG. 4; I

FIG. 12 is a sectional view-on a larger scale of the mold end wall or'plu'g; and

FIG. 13 is .a fragmentary sectional view illustrating an alternative to that of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In theform of FIG. 1 there is illustrated a casting ladle 10 from which a molten metal stream 12 flows into a tundish 14 which is lined with any suitable heatresistant material. 16. such as a ceramic material. The metal may be steel orlits alloys, iron o'r'its alloys, or

nickel or its alloys, for example. The process only lends itself to casting those metals which because of their relatively low thermal conductivity (i.e., less than 0.25 calories/sq.cm./cm./C/sec., near room temperature) have the capacity to form a self-supporting skin or shell which has the strength to contain within itself the liquid metal from which the skin is formed. Such materials are known as skin formers. For example, high thermal conductivity materials such as copper and aluminum do not have this ability, as-the thermal gradient between the outer surface of the shell and the liquid material is insufficientto allow a shell to formwhich 'is strong enough to prevent the liquidin the core from rupturing the-shell. The tundish 14 has a stopper rig 18 to allow the flow of molten metal 20 through a nozzle I 22. A hollow starting bar 24 is fixed to the nozzle 22 in any suitablev manner at one end of the bar. The other end of the bar 24 is tapered as illustrated and has formed therein peripheral grooves 26. At the commencement of a casting operation the last-mentioned tapered end of the starting bar 24 is disposed in the cooled closed endmold, indicated generally at'28, in

the mold position shown in broken lines in FIG. 1.

The tundish 14 rests on'a stationary base 30 in the illustrated form of I the inventionand from which'base track 32 extends to support a mold transport carriage 34 on wheels 36. The carriage 34 has thereon a support 37 forthe mold 28. The mold 28is-supported on the support 37 for a rectilinear sliding or oscillating movement thereon in a direction length-wise ,of the track 32. Suchsliding or oscillating movement is imparted'to the mold by a mold oscillator 38 connected to the mold by a rod 40. The oscillator38 is supportedby the carriage 34 in fixed relation thereto. I The carriage 34 is drawn to the right as viewed in FIG. 1 by a bar 42as an article iscast which article is illustrated as a billet which. maybe structured of a single metal. However, itis to be'understood that while the billet which is cast maybe of the single metal type illustrated and described in U.S. Pat. No. 3,517,725, supra, the article cast may be a composite metal billet or a length of metal tubing as described and illustrated in my US." Pat. Nos.*3,625,277'and 3,680,624, respectively supra, hereinafter also referred to: as a billet. Casting supports 44- shown in lowered positions, :are raised to support the billet as it is cast and the mold28 moves to the right as viewed in FIG. 1.

Thev mold28 comprises an axial wall structure provided by a longitudinally arranged annular element 46 preferably formed of copper and whichis jacketed for thezflow of a coolant liquid therethrough. The jacketed wall structure has inlets 48 for a coolant liquid such as water and outlets 50so that the coolant is circulated through the jacket. The wall which closes theend of the mold'remote from the tundish is indicated at 52. This wall' is'constructed of a material having a substantially higher melting point than the metal which is being cast. For example, if the metal being cast is steel, the wall.52 may be structured of "molybdenum but is" advantageously constructed of a ceramic material as illus trated. A thermal insulating ring 54 is interposed between the end wall 52 of the mold and the cooled axial wall structure 46 of the mold. This thermal insulating ring maybe formed of the same c'eramicmaterial as the end wall 52 ormay be formedof a ceramic material having higher thermal insulating properties such as aluminum oxide or Zirconium oxide. Obviously, if the element S4 is formed of the same material as the end wall 52, the element 54 may be formed as an integral part of the end wall 52'. w

- At least a region of the end wall 52 is heated by external means other than molten material flowing into the mold such as steel to reduce oreliminate the formation of a membrane as aforesaid for the aforesaid reason. For this purpose, a suitable fuel may be burned in a region external to the mold cavity but close to the wall 52 to supply the heat; One alternative means for the supply of heat is the use of electrical resistance coils in the last-mentioned 'regionof themold structure'ln the illustrated form, the mold end wall 52 is heated by an inof tubing, has a coolant inlet 58 and a coolant outlet 60 for. the circulation of a coolant liquid such as water therethrough to prevent the induction heating coil from melting.

The body of the induction heating coil 55 is disposed in a clearance opening in the mold end wall 52, as shown in FIG. 1, which space is indicated at 62 and is of annular form surrounding the boss portion 56. It is believed made clear from the foregoing that the boss portion 56 exists solely to facilitate the heating of the wall 52 in the illustrated form of the invention and may be omitted where other types of heating are utilized to take the place of that illustrated. It will also be understood from the foregoing that the wall-heating boss portion 56 may be formed in one piece with the mold end wall 52, not shown, where the wall 52 itself constitutes a satisfactory electrical conductor for induction heating. In the illustrated form of FIG. 1, the mold 28 includes a retaining plate 64 which sandwiches the graphite portion 56 of the end wall 52 between the latter and the plate 64, which plate 64 may be bolted, as at 66, to an endflange 68 of the axial mold wall structure 46, as shown in FIG. 1.

In the form of FIG. 1, a billet is cast in the following manner. Molten steel from the tundish l4 flows through the hollow starting bar 24 from the nozzle 22 into the closed end mold 28 in the broken-line mold position of FIG. 1. The starting bar 24 may be preheated metal through the starting bar. The molten metal,

under the influence of the cooled axial wall structure 46 of the mold, solidifies around thetapered end of the bar 24 and adheres to the bar assisted by penetration into the peripheral grooves 26 thereof. It is believed made clear that means other than the grooves 26 may be utilized for adherence of the solidifying metal to the bar 24, as by holes or projections onthe latter, for example. i

At least a part of the .end wall structure 52 of the mold is at least preheated to limit or eliminate the formation of a membrane of the casting material thereon. If the casting material is a grade of carbon steel which has a melting range of approximately 2,7352,8 10 F, it starts to solidify at a temperature below or approximately at 2,810F. At approximately 2,735F this material is substantially solidified. For such steel, the mold end wall 52 is preferably heated to approximately 2,200 F, a temperature indicated to be below the solidification point of the metal.

It is believed unnecessary to heat the mold end wall 52, as aforesaid, to the melting point of the material being cast inasmuch as heat is transferred to the mold end wall by the material being cast and the temperature of the mold end in the region exposed to the molten metal is raised by the molten metal to the point where the formation of a solidifying membrane on the wall 52 is efiectively limited or entirely eliminated.

When the mold end in the region exposed to molten metal is in substantially full contact with such molten metal, and the temperature of the exposed surface of the last-mentioned mold region has been raised as described, the application of heat by the coil 55 may be terminated, provided the temperature of the lastmentioned surface does not drop sufficiently to allow such membrane formation. It is believed made clear from the foregoing that overheating of the end wall structure 52 is to be avoided. On the other hand, heat dissipation from the end surface of the mold cavity must be limited during casting to limit the formation of such a membrane. The thermal characteristics of the end. wall structure of the mold may limit heat dissipation sufficiently. If such thermal characteristics are not existent, then additional heat must be supplied to the end surface of the mold cavity, as by the heating coil, to limit heat dissipation.

When the mold cavity is filled with molten metal such as steel for example, the transport carriage 34 is moved to the right as viewed in FIG. 1 as a solidified casting shell 72 of a billet is formed with a molten core or center 74. The shell 72 is formed under the influence of the cooled axial wall structure 46 of the mold. As the mold 28 continues to move to the right, molten metal continues to flow from the tundish through the molten center 74 of the billet and forms a continuation of the casting shell 72 at the end of the billet remote from the tundish 14.

The oscillator 38 supported on the carriage 34 may be utilized to move the mold in discrete steps during the casting operation. The operating rod 40 of theoscillator 38 may be connected to a flange 78 connected to the retaining plate 64 of the mold. Oscillation of the mold 28 reduces the tendency of the billet to adhere to the mold. In the event there is a tendency for hot tearing to develop in the outer surface of the billet shell within the mold, such mold oscillation over such tears,

that is, on movement toward the tundish, allows such tears to' mend within the mold.

As shown in FIG. 1, the solidified shell 72 is thinnest at the extremity of the a'xiallmold wall structure 46 nearest the mold end wall 52. The shell 72 thickens progressively along a portion thereof extending in a direction towardthe tundish 14. FIG. 1 also illustrates the solidifying shell 72 as progressively shrinking away from the axial mold wall structure 46in a direction toward the tundish 14. The cooled axial wall structure 46of the mold has sufficientexposure to the billet shell 72 so that the latter cools and solidifies to resist ferrostatic pressure.

As the solidified shell exits from the mold 28 it is impinged by sprays of coolant liquid such as water from nozzles which further cool the billet in the'solidification process. Only two such nozzles are illustrated by way of example and indicated at 76. As the forming billet extends from the mold 28 in a direction toward the tundish 14 it is supported by the supports 44 previously described, which are elevated from the lower position shown in FIG. 1 to raised positions in which the supports 44 are operative to engage and render support for the billet being cast as it exits from the mold 28.

In the modification of the invention shown in FIGS. 2 and 3, the mold, indicated generally at 80, is in many respects similar to the above-described mold 28 as will be apparent hereinafter. For example, it has a cooled axial wall structure and a heated closed end. The mold is, supported in a similar fashion on a stand 82 of a car-.

wall structure 86 remote from the tundish. The tie rods 90 may be secured-to the crosshead 92 as by nuts 94.

The standard 88 fixedly supports in upwardly spaced relation from the carriage 84 an oscillator 96 operating a horizontally arranged rod or plunger 98 extending through the crosshead 92 and secured thereto as by nuts 100. Operation of the oscillator 96 effects axial oscillation of the axial wall structure 86 of the mold structure on the support 82 provided on the carriage. In FIG. 2, it is indicated that the mold element 86 may be oscillated as aforesaid from the full line position thereof to the broken line position shown in this view, which oscillation in itself reduces adherence of the billet to the mold. The closed end wall of the mold, which is of a composite structure, which will be described in detail hereinafter, is held in stationary relation to the carriage 84 by a construction to be described hereinafter.

The closed end of the mold 80 includes an annular manifold 102, which may be structured of copper, hav ing a fit within the axial wall structure 86 of the mold which permits the latter to have sliding engagement therewith'in its aforesaid oscillating movement. Within the manifold 102 and closing the axial opening therethrough there is a wall part 104 of the mold wall similar to the wall part 52 previously described and which may be formed of ceramic material. As best shown in FIG. 3, the manifold 102 may be provided with an annular shoulder 106 which retains the wall part 104 from dislocation in a direction toward the tundish.

A' boss portion 108 extends rearwardly from the wall part 104 in the central region thereof, and the boss portion 108 extends into a forwardly facing recess in a block 110. The last-mentioned block also extends into the central opening in the manifold 102, which block 110 may be formed of ceramic material as shown. The boss portion 108 may be formed of graphite and is similar in construction and functionto the graphite element 56 of the mold form of FIG. 1. A retaining plate 112 ex- I tends across the central opening in the manifold 102 rearwardly of the block 110 and is suitably secured to the manifold 102 by fasteners not shown.

As shown in FIG. 2, an annular opening is provided around the boss portion 108 in which there is supported the body of an induction heating coil 114 similar to the induction heating coil 55 previously described. The induction heating coil has a coolant inlet 116 and a coolant outlet 118 for the circulation of a coolant liquid through the coil 114. As shown in the lastmentioned view the inlet 1'16 and the outlet 118 extend through the block 110 and the retaining plate 112.

The forward extremity of the manifold 102 may have an annular surface 120 (FIG. 2) extending intermediate the near surface of the axial wall structure 86 of the mold and an inwardly tapered annular surface 122 of the manifold 102 which last-mentioned surface extends toward the wall part 104. The tapered surface 122 facilitates the separation of a casting from the mold 80 subsequent to the casting operation. As shown, the surfaces 120 and 122 of the manifold 102 both define portions of the mold cavity.

The manifold 102 is provided for the distribution of a lubricant under pressure. The manifold 102 has at least two axially spaced radially extending chambers 124 of annular form which are best shown in FIG. 3. The chambers 124 are open to the near surface of the axial wall structure 86 of the mold, which surface slides over the periphery of the manifold 102. The chambers 124 are interconnected by branches of an axial duct, 126 which axial duct extends through the rear end of the manifold 102 for connection to a tube 128 extending'through the retaining plate 112 and connected to the outlet of a suitable pump 130, which pump has an inlet connected to a tube 132 extending into a reservoir 134 of a liquid lubricant.

As shown in FIG. 3, a pressure gage 136 is connected to the tube 128 downstream of the pump 130. There is also connected to the tube 128 a tube 138 which bypasses the pump 136 and has an outlet connected to a pressure-relief valve 140, the outlet of which valve is connectedto the inlet of a tube 142 which has an outlet to the reservoir 134.

A resilient annular sealing element 144 is disposed in the rearmost lubricant chamber 124 for sealing engagement with the near surface of the axial mold wall structure 86. The sealing element 144 may be structured of a suitable elastomer and have the cross section shown by way of example in FIG. 3. A similar sealing element 146 is disposed in the foremost lubricant chamber 124 but differs from the sealing element 144 in that it has a series of circumferentially spaced radial openings 148 extending therethrough for the escape of lubricant through the element 146.

The seal 146, which is useful for compensating for dimensional changes in the manifold 102 and the axial wall'structure 86 of the mold, may be omitted if desired. Lubricant from the forward chamber 124 passes between the oscillating axial mold wall structure 86 and the above described end wall structure of the mold and is introduced as a thin film, during the oscillation of the wall structure 86, between the last-mentioned wall structure and the solidifying casting shell 72. I

As it is desirable to introduce the lubricant between two cooled surfaces to prevent immediate vaporization or burning off of the lubricant in the mold onvits introduction, the manifold 102 is cooled by water circulating in an annular chamber 149 formed in the manifold 102, which chamber is illustrated as supplied by an axial duct 150 connected to a water inlet tube 152 extending through the retainer plate 112. The annular chamber 149 has a similarly configured water outlet not shown.

As previously indicated, the end wall structure of the mold, which includes the manifold 102. and the end wall part 104, is maintained stationary with reference to the carriage 84 during the casting operation. For this purpose, a plurality of tie rods 154. are shown, each 1 having one end threaded into the retainer plate 112 and having the other end thereof secured tothe standard 88, as by a flange 156 and a nut 158, the flange bearing against one face of the standard and the nut bearing against the remote face of the standard.

In operation of the apparatus including the mold illustrated in FIGS. 2 and '3, molten metal, such as steel forexample, flows into the closed end mold from the tundish in the manner previously described with reference to the mold of FIG. 1. Molten metal commences solidification on contact with the cooled axial mold wall structure 86 to form the shell 72 of the billet while the center or core 74 of the billet remains in a molten state as the mold 80 and the tundish are separated during the casting operation. The end wall structure of the mold 80 is heated in the manner indicated with reference to the mold of FIG. 1 to limit or eliminate the formation of a solidifying membrane on the end wall structure of the mold, as indicated in FIG. 2.

It will be apparent from the last-mentioned view that the separating movement of the mold 80 from the tundish is accomplished by movement of the mold carriage 84 to the right in this illustrated form. As the mold is moved in this manner the billet is elongated. The end wall structure of the mold, which includes the wall part 104, is maintained stationary with reference to the carriage 84 through the support rods 154 and the standard 88 affixed to the carriage. While the casting operation proceeds, the oscillator 96'is operated and, through the rod or plunger 98, the crosshead 92 and the tie rods 90, oscillates the axial mold wall structure 86. It is believed made clear from the foregoing that during such oscillation the axial mold wall structure 86 slides on the support 82 of the carriage 84.

On operation of the oscillator 96, the inner surface of the axial mold wall structure 86 picks up afilm of lubricant on its rearward travel, that is, ina direction away from the tundish, from the forward lubricant chamber 124 in the manifold 102. The seal 144 in the rearward chamber 124 effectively tends to prevent the escape of this lubricant between the manifold 102 and the axial wall structure 86. On the forward oscillating stroke of the axial wall structure 86, the film of lubricant previously deposited in the aforesaid manner is carried into the mold cavity to extend between the axial mold wall structire 86 and the billet being formed in the mold cavity. The film of lubricant covers that portion of the mold cavity in which there is the greatest tendency of the billet to adhere to the mold, that is, in the region adjacent the end wall structure of the mold. Such lubrication effectively resists the tendency of the billet to adhere to the axial mold wall structure, while limiting contamination of the metal being cast.

The lubricant supplied under pressure by the pump 136 from the reservoir 134 may consist, for example, of rapeseed, silicone or cranbee oil or may have a base formed from artificial slags or from powders such as ceramic and/or metallic powders. v

The operation of the lubricating manifold 102 during the casting operation is believed made clear from the foregoing. The pressure of the lubricant in the axial duct 126 is sufficient to normally provide an effective seal between the rearmost sealing element 144 and the axial mold wall structure 86. If desired, a separate pressure system, not shown, may be employed for this purpose.

The lubricant pressure in the illustrated system may be predetermined to be dependent on the changing head of metal in the tundish during a casting operation taking into account the metal in the mold cavity. Obviously, the pressure of the lubricant must be sufficient for the lubricant to enter the mold cavity. The pressure of the lubricant may be controlled by the head of metal in the tundish as in my U.S. patent application, Ser. No. 878,956 filed Nov. 21, 1969, wherein there is described a technique for varying the pressure of a gas introduced into a mold during a continuous casting operation.

The aforementioned pressure-relief valve 140 of the lubrication system is provided to open in the event of excessive gas or lubricant pressure in the mold. Excessive gas may escape from the mold cavity between the axial mold wall structure 86 and the end wall structure of the mold. When the valve 140 is open, lubricant in the system may escape through the valve through the tube 142 to return to the reservoir 134.

In the forms of the invention illustrated in FIGS. 1 and 2 hot water may be flowed through the respective jacketed axial wall structure of the mold 28 or the mold prior to the commencement of a casting operation to effectively reduce or eliminate any condensation on the inner surface of the axial wall structure of the mold. In fact this is the preferred technique. The reason for this technique is that if any condensation is trapped in the mold on entry of the molten metal therein at the commencement of the casting operation the mold may be damaged and there may be other injury.

Also, in the forms of the invention illustrated in FIGS. 1 and 2, thetechnique of heating the plug or closed end of the mold is improved over that of the technique described in the particular method of continuous casting illustrated in my aforementioned US. Pat. No. 3,517,725 wherein the rupture of any metal membrane on the plug or end wall is assisted by the generation of heat within the mold cavity. Generation of heat within the mold cavity may contaminate the mold. In accordance with the above-described forms of the in stant invention no contaminant is introduced into the mold cavity for the heating of the plug or end wall as aforesaid. Whether by induction heating, fuel burning or other forms of heating generation, the heat generation is external to the mold cavity. This is a significant advantage in the continuous casting of a metal.

Referring now to the modification of the invention shown in FIGS. 4-11 and with particular reference to FIGS. 4-7, which last-mentioned figures of the drawing illustrate the major elements of the apparatus and their general orientation with respect to each other, the tundish is indicated at through which molten steel flows through exit nozzle 174 during a casting operation. The tundish is illustrated as stationary and the nozzle 174 has associated therewith and in fixed relation thereto a starting bar device (see FIG. 4) indicated at 176. FIG. 4 illustrates the preheating operation prior to a casting operation. There is provided an axial wall structure 184 of a mold similar to the previously described water-jacketed axial mold wall structure 86 which is fixed to a support 182 rectilinearly movable as on a track 183 for movement toward and away from the tundish 170.

As in the form of FIGS. 1 and 2 previously described, a wall structure is provided to close the end of the axial wall structure of the mold during a casting operation. In the form of the invention under discussion this wall structure is provided by a plug which is movable axially within the axial wall structure 184 of the mold. A carriage 204 is provided for the plug 190 which carriage may ride on the same track 183 as the support 182 and must be in axial alignment therewith in its movements. The carriage 204 has a vertical standard 202 fixed thereon to which is attached in fixed manner a fitting 196 from which protrude, in fixed relation toward the axial mold wall structure 184 in spaced parallel relation, hollow rods 192, 194. Rods 192, 194 are also fixed to the plug 190 at their ends remote from the ends of the rods 192, 194 fixed to the fitting 196. The carriage 204 may be moved toward and away from the tundish 170 by any suitable drive means acting on the carriage as through push-pull rod 203 to effect the aforementioned rectilinear movement of the carriage 204. Such movement of the carriage 204 effects similar 1 1 I movement of the plug 190 as willbe made clear from the foregoing.

Also fixed to the carriage 204 is a vertically-arranged standard 205 spaced rearwardly from the standard 202 as indicated. Standards 202 and 205 journal a screw 208 extending therebe'tween and driven from a drive mechanism, indicated generally at 210, first in one di- A non-angularly movable carriage 206 is provided to move axially of the carriage 204 to effect all movements of .the axial wall structure 184 with. reference to the-closed 'mold end or plug 190 and a separate movement of the structure 183 from the position of FIG. 4 to the position of FIG. 5. The carriage 206 is inthe form of a yoke (best shown inFIG. 11) having in the central-region thereof a nut 201 internally threaded to cooperate with the threads of the screw 2 08. Rods 199, in spaced parallel relation to one another, each have one end thereof secured to the near end of the axial wall structure 184 and extend through holes in the standard 202 (one illustrated rod 199 extending through a larger hole in the standard 205) and illustrated holes (FIG. 11) in the yoke 206 so as to be slideable in such holes. Each rod 199 terminates in an enlargement 211 at-theleft-hand end as viewed in FIG. 4 for example.

When the axial wall structure 184 and the end wall or plug 190oc cupy the relative positions to the tundish 170 shown in FIG. 4, which is the preheating condition of the apparatus, the rods 199 extend rearwardly or to the left of the carriage 206 a distance as shown. When the axial mold .wall structure 184 and the closed end or plug 90 of the mold occupy the relative positions to the tundish shown in FIGS. 6 and 7 which respectively illustrate the last stage of thecommencement of the casting operation and the casting of an article utilizing the apparatus of the invention, the rod enlargements 211 are in proximity to the carriage or yoke 206, and it will be noted that the enlargements 211 are sufficiently large that they will not pass through the carriage or yoke 206.

In the illustrated form under discussion, it is necessaryto couple the carriage 206 to the axial wall structure 184 to move the last-mentioned wall structure with reference both to wall or plug 190 and to the tundish, that is from the position of FIG. 4 to the position of FIG. as previously indicated. Any suitable mechanism may be employed for this purpose. In FIGS. 4-7, there are shown by way of example sleeves on' the respective rods 199 which sleeves are indicated at 213 and which sleeves are slideable'on the rods 199. Coil springs 215 are disposed on the respective rods 199 between neighboring ends of the sleeves 213 and the mold in such manner that when the sleeves have a sliding movement on the rods 199 in a direction toward the axial wall structure 184 the springs are compressed and resiliently urge the axial wall structure 184 toward the tundish 170. The movement of the sleeves 213 on the rods 199 in the aforementioned manner will be made clear hereinafter. i v

The other ends of the sleeves 213 are of an outer diameter such that they will slide through the standard 202 but will not slide through the carriage 206,and will abut the carriage when the screw 208 is driven ina direction to drive the carriage forwardly toward the tundish 170 by the drive mechanism 210. The carriage 206 during such movement abuts the last-mentioned ends of the sleeves and through these sleeves and the springs 215 the axial wall structure 184 is moved from the preheating condition of FIG. 4 to the position of FIG. 5 wherein the forward end face of the axial wall structure 184 abuts, the tundish 170, meaning that the lastmentioned face of the axial wall structure 184 abuts a generally vertical surface, best shown in FIG. 9 and which will be described hereinafter with reference thereto,'which is fixed to the exit end of the tundish nozzle 174 and may be considered for this reason a part of the tundish 170. I t

It is believed made clear from the foregoing that the carriage'204 has a longitudinal movement and in its movement forward and back or toward and away from the tundish 170 carrieswith it the plug l90.,Th'e carriage 206 mounted on the carriage 204 likewise has-a longitudinal movement lengthwise of the carriage 204 to advance the axial or wall structure 184 toward the tundish as aforesaid. r

"As illustrated in FIGS. 4-7 and 11 the carriage or yoke 206 is provided with spring latchesor detents 220 for association with the respective aforementioned mold rods 199. Each detent 220 has a conical or tapered endto enter complementally shaped cavities 222 in the respective mold rods 199 adjacent the respective enlargements thereof. The last-named conical or tapered endis formed on a plunger 224 of each detent 220. Each plunger224 has an enlarged portion as illustrated and a reduced portion extending through a cap 226 in fixed-position to the yoke. A coil spring 228 (FIG. 11) on the plunger 224 of each detent is compressed between the enlargement of the respective plunger 224 and the respective cap 226 urging the plunger in a direction to engage and latch in the respective cavities 222. 'Any suitable means may be provided to retract each plunger 224 from the respective cavity 222, such as by manipulation of the handle portion 230 of each detent plunger, shown for'purposes of example.

only.

The detents 220 are latched only when the wall or plug reaches the position of FIG. 6 from the position of FIG. 5 and thereafter during the casting operation as illustrated in FIG. 7. When the detents 220 are latched, oscillation of the axial mold wall structure 184 may be commenced. The support 182, fixed to the wall structure 184, is also oscillated. The oscillation of the axial wall structure 184, which continues until the end of a casting operation, is similar to that described with reference to the modification of the invention shown in FIG. 2. y i

The drive mechanism for the screw 208 which effects the aforesaid axial movement of the carriage 206 will now be described. Affixed to the rear end of the screw 208 extending to the left (FIGS. 4-7) of the standard 205 is a-gear 232 for simultaneous drive from meshing spur gears 234 which spur gears are driven by respective motor shafts 236. The motor shafts are-driven simultaneously by non-illustrated reversible, variablespeed motors. It is believed made clear from the foregoing that the shafts 236 are driven to effect movement of the carriage 206 to advance the axial wall structure 184 of the mold from the position of FIG. 4 to the posi tion of FIG. 5.

The construction and arrangement is such that when the carriage 206 is latched as aforesaid to the mold rods 199 and the drive of the carriage 206 is in a direction to impart movement to the axial mold wall structure 184 in a direction away from the tundish 170 during the aforesaid oscillation operation, this movement is faster than the withdrawal rate of the mold from the tundish.

The withdrawal of the mold during casting, which may be effected by any suitable means, is illustrated as through the bar or rod 203 which may be pulled to effect such withdrawal and which rod 203 is pushed to bring the mold structure up toward the tundish 170 preliminary to a casting operation. While it has been stated that the carriage 204 withdraws the mold from the tundish, which mold of course comprises the axial wall structure 184 and the end wall or plug 190 it is evident from the foregoing that this is true because the carriage 206 for the axial wall structure 184 is carried on the carriage 204.

While in the form of the invention illustrated by way of example in FIGS. 4-12 the axial wall structure 184 of the mold is not moved in a rearward direction until the closed end wall or plug 190 reaches the illustrated rearward position of FIG. 6, circumstances may not warrant withdrawing the axial wall structure 184 at that time. Circumstances may arise which do not require this. On the contrary, the invention contemplates the alternative of withdrawing the axial wall structure 184 either before or after the plug 190 reaches the rearward position shown in the last-mentioned view, as well as withdrawing the axial wall structure 184 by the carriage 204 as aforesaid at the time the closed end wall or plug 190 reaches the position of FIG. 6.'

Returning to the oscillating movement of the axial wall structure 184 of the mold during casting which is illustrated in FIG. 7, the axial wall sructure 184 should be oscillated in a particular 'manner. If it is assumed that the mold transport carriage 204 is being moved away from the tundish 170 at a casting rate of 36 inches/minute, the mold should be oscillated at a rate greater than 36 inches/minute for a given number of cycles/minute which, for example could be cycles/- minute. As the mold moves toward the tundish during oscillation, at a rate for example of 40 inches/minute, while the transport carriage 204 moves away from the tundish at a rate of 36 inches/minute, the axial wall 184 will have a net velocity of 4 inches/minute in the direction of the tundish. This movement of the axial wall structure 184 toward the tundish creates compressive forces in the solidifying skin or shell of the casting and will effectively tend to reduce or eliminate rupturing of the skin. If the axial wall structure movement in the direction away from the tundish is at the rate of 40 inches/minute its net velocity away from the tundish will be 76 inches/minute in that direction.

The tundish 170 is provided with an overflow at 172 and a drain which is normally closed by a plug 173. During this period a cover 178 extends over and rests on the mouth of the tundish. And the outlet end of the nozzle 174 is free and open. Conduit 180, which may be fixed to the tundish cover 178, has an outlet end opening within the cover as shown and has a nonillustrated inlet end connected to a source of fuel gas under pressure which fuel gas bums within or below the cover 178 in the preheating operation, the hot gases of which emerge through the open free end of the nozzle 174 and impinge upon the near face of the plug 190.

These hot gases seen impinging on the lastmentioned face of the plug 190 in FIG. 8 preheat that face of the plug 190 while concurrently preheating the tundish. The axial wall structure 184, which is water jacketed, includes a water inlet 186 and a water outlet 188, and it is to be understood that the inlet 186 is in fluid flow communication with the outlet 188. In the preheating operation, the plug 190 is located within the end portion of the axial wall structure 184 of the mold and may protrude therefrom as shown in FIG. 8.

In the preheating operation, the plug 190 is not only spaced from the nozzle 174 of the tundish but is also spaced from the starting bar device 176. As previously indicated, the starting bar device 176 is used for only a single casting and is therefore detachably secured to the nozzle 174. The device 176 includes a plate or similar element 240 having an opening 242 surrounding the discharge opening of the nozzle 174. Within the nozzle there is fitted a ceramic tube 244 configured and arranged according to FIG. 8. This tube extends into the opening 242 and may abut the plate 240.

Fingers 246 project rearwardly from the plate 240 toward the plug in fixed relation to the plate 240. Only two such fingers 246 are shown and it is preferred to employ at least four arranged circumferentially around the opening 242, which fingers are so positioned on the plate or element 240 that, when the axial wall structure 184 is in the position of FIGS. 5 and 9, the fingers extend within the cavity formed by the axial mold wall structure 184.

In this illustrated form the fingers 246 take theform of bolts protruding from the element 240 rearwardly towardvthe plug and are provided with heads at the ends thereof nearest the plug. Lock nuts or seals 248 are received on respective ones of the bolts 246 to abut the element 240 in the manner shown in FIG. 8 for example. As shown in the last-mentioned view, the bolts 246 extend through a flange 252 of the nozzle 174 and the forwardly protruding parts thereof respectively re ceive bolts 250 threaded down on the aforementioned flange.

During the preheating operation under discussion, hot water may be circulated through the jacketed axial wall structure 184 (and/or the fluid system 29.8, to be described hereinafter, in the plug to remove condensation from the internal surface thereof which bounds in part the mold cavity produced at a later stage. At least during the preheating operation, the plug 190 may also be preheated, that is separately and apart from the generation of heat on the face thereof nearest the tundish, by a technique such as'illustrated and described with reference to the form of FIG. '2, but preferably the plug 190 has a construction similar to that shown in FIG. 11 to be described hereinafter.

On completion of the preheating of the tundish and the plug 190, the axial wall structure 184 of the mold is advanced as aforesaid by appropriate movement of the carriage 206 under the control of the drive mechanism 210 until the rear end face of the plate element 240 is abutted at which point such advancing move ment of the wall structure 184 ceases as by operation of non-illustrated limit switches which operate the nonillustrated motors driving the respective shafts 236.

Substantiallyconcurrently therewith, or prior thereto, the cover 178'is removed with the conduit 180 from the tundish 170at which time the apparatus is in the condition of FIGS. and 9. 7

As shown in FIG. 9, molten metal substantially fills the tundish. 170 which differs from the form of the tundish shown in FIG. 2 in its internal design as indicated in FIGS. 8 and 9, and is without a stopper rig. The molten metalto be cast may be one of a wide variety of metals, such as steel and its alloys or iron, for purposes of example only. Such molten metal received in the tundish 170, and maintained substantially at a preferred height therein, exits from the tundish through the nozzle 174 and flows around the aforementioned fingers'246 to which the molten metal subsequently adheres so that the fingers 246 of the starting device 176 act as a starting bar to draw metal from the mold as will be explained more fully hereinafter.

As shown in FIGS. 9 and 10 spray nozzles 260 for a coolant are carried by the axial wall structure 184 of the mold and move therewith as indicated in FIG. 10. In the condition of FIG. 10 the nozzles 260 are operative. In the condition of FIG. '9, the wall or plug 190 is shown'spaced rearwardly a distance from the starting device 176 but may be in fairly close proximity thereto. As the axial wall structure 184 and the plug or end wall 190 form together a mold cavity, shown in one condition in FIG. 9, the mold cavity is enlarged or lengthened as the end wall or plug 190 moves on the carriage 204 from the position of FIGS. 5 and 9 to the positions of FIGS. 6 and 10. on reaching theplug position shown in FIGS. 6 and 10, the mold rods 199 are latched as aforesaid to the carriage 206 for oscillation of the axial wall structure 184 as aforesaid.

On rearward movement of the carriage 204 from the position of FIG. 6 toward the position of FIG. 7, the

mold with the elements thereof in the condition of FIG.

' 6 are retracted together or moved away from the tunwallstructure 184 is cooled by the circulation therethrough of water and non-illustrated water jets (in addition to those issuing from nozzles 260) impinge on the lengthening casting, particularly the peripheral surface of the shell of the casting, all as previously described. As the casting is elongated suitable supports, as in FIGS. 7 and 10, (not shown) which may take the forms of pads similar to the pads 44 previously described, may be raised to provide adequate support for the casting with a molten core 26lb.

In FIG. 12, there is illustrated one preferred form of the wall or plug 190. The plug 190 has a cavity 290 therein defined by a tubular part 192 structured of a metal such as copper. Theforward end of the part 192 may be circumferentially tapered as at 294 and provide also a circumferentially rearwardly-facing abutment shoulder 296. The part 192- has a coolant distribution system indicated generally at 298 for the flow of a fluid such as water. Spaced apart along a portion of its periphery, the part 192 receives bearing elements 300 which bear against the internal surface of the axial wall structure 184. The bearing elements 300 encircle the part 292. I

In proximity to the forward end of the element 292, which constitutes the forward end of the plug 190, there is mounted in a peripheral groove 304 in the part 292 an element 302 which may be formedin sections, like the bearing elements 300, to extend around the peripheral surface of the plug part 292 which element 302 serves a dual function both of which are important. One such function is to provide a lubricant between the plug and. the axial wall structure 184 of the mold. The other function is to provide an effective seal to prevent metal in the mold cavity from being introduced between the plug 190 and the axial wall structure-184 of the mold for a substantial distance, if any. The element 302 or its sections are urged outwardly or toward the axial wall structure 184 from the groove 304 by a plurality of compression springs 305 between the bottom of the groove 304 and near the face of the element 302 which springs are illustrated by'way of example only. v

' The element 302 may be rigid as shown and be structuredof amaterial such as boron nitride or graphite for example but it is not critical that the element 302 be formed as a rigid member. The element 302 could be formed as an expansible member or resilient member,

provided that it serves the aforesaid dual functions. While in the form illustrated in FIG. 11 by way of example, the element 302, which has a high wear rate, is spaced a short distance rearwardly from the leading edge of the plug part 292 it may in fact be formed in the leading edge of the plug 190, if desired, and still coact with the plug 190 and the axial internal wall surface, and still be urged as by a spring in a direction to abut the last-mentioned wall surface.

Closing the rear end of the plug part 292 is a composite platei-like structure indicated generally at 3.10. This end plate 310 has a conduit portion 312 formed therein and a similar conduit portion 314. The conduit 312 couples the conduit, formed by the hollow tube or rod 192 previously described, to the inlet of the fluid coolant distribution system 298 while the conduit 314 couples the .outlet of the last-mentioned system to the conduit formed by the hollow tube or rod 194 previously described, which tubes or rods have their corresponding ends suitably fixed to the plate 310.

Also as previously described, the other ends of the hollow tubes 192, 194 are fixed to the fitting 196 of FIG. 4 and in fluid flow communication with the inlet 198 for a coolant such as water and fluid communication with the outlet 200., respectively. The construction and arrangement is such that the coolant may be continuously circulated through the coolant distribution system 298 to cool the plug part 292.

The composite plate 310 has a bore which is threaded and which extends through the central region of the composite plate 310 from front to rear, and which threaded bore receives a threaded 'plug, 316 which plug 316 is structured for threaded adjustment of the plug in thethreaded bore of the composite plate 310. The plug 316 has a forwardly opening axial socket 317 therein. A plunger 318 is extensible into the socket 317 of the plug 316 in the mannershown in FIG. 12, and as there shown protrudes from the socketed plug. The plunger 318 is urged outwardly or forwardly from the plug 316 by a compression spring 320 bottoming in the socket of the plug 316 and against the rear end of the plunger 318. The composite plate 310 is secured in any suitable manner to the near end of the plug part 292 so that'the composite plate 310 may be removed when desired for a purpose which will appear hereinafter.

Within the tubular part 292 and abutting the shoulder 296 is a ceramic plate 322 which is disposable and may be replaced after each casting operation if required, upon disassembly of the composite plate 310 fromthe tubular part 292. In other words, it may be removed from the plug 190 through the rear end of the part 292 when the composite plate 310 is detached. A channelled ceramic'plate 324 receives therein a relatively long helical, electrical resistance coil 323 electrically connectedin any conventional manner, which is sinuously bent to be received in the aforementioned channelled plate 324. Plate 324 has its channelled side abutting the ceramic part 322, and fillers in the form of ceramic plugs 325, 326 lie rearwardly from the plate 324 and abut one another in the manner shown in FIG. 12. Rearwardly of the filler part 326 and abutting the rear face of the part 326 is a stainless steel plate part 328, which plate part is engaged by the forward end of the plunger 318 which holds the parts 322-328 assembled and in the pressed-together condition shown in FIG. 12.

FIG. 13 showsan alternative starting bar construction whichmay be used in place of the starting bar device 176 shown in FIGS. 4 and 8, for example. The starting bar of FIG. l3may be considered more desirable than that of the form of FIG. 4 in that it does not extend at all into-the mold cavity, and therefore inhibits contamination of the cavity and any possible breakage of the starting bar within the cavity. In the form of FIG. 13, the flange 327 of the tundish exit nozzle 174 has secured thereto, as by bolts 328, a plate 330 having in the rear face portion thereof, that is the face directed away from the tundish 170, one or more grooves therein also facing rearwardly or opening rearwardly through the rear face of the plate 330.

Only one such groove is indicated at 332 and is generally of dovetail form in cross section or undercut as illustrated in FIG. 13 so that when molten metal enters such groove 332 and subsequently solidifies it cannot thereafter be removed from the plate 330 during the casting operation, so that the plate 330, grooved in this manner, forms a starting bar device similar in purpose to the starting bar device 176 previously described. The groove 332 is shown as having an annular configuration. but it might be of spiral form for example, if desired. In the condition of the apparatus shown in FIG. 13, the

near end of the axial wall structure 184 is shown engag-' ing in the flatwise relation the plate 330. The plate 330, is, of course, of larger outer diameter than the internal diameter of the axial wall structure 184, and the groove 332 is exposed to the interior of the axial wall structure.

It is believed made clear from the foregoing that the stated objects of the invention are achieved.

While several embodiments of the method and apparatus for continuous casting have been illustrated and described, it will be apparent to those versed in the art that the invention may take other forms and is susceptible of various changes in details without departing from the principles of the invention.

What is claimed is:

l. A process of continuously casting an elongated metal article, comprising the steps of: introducing molten metal from a source of molten metal into a mold having an axial wall structure and a closed-end wall structure, defining a mold cavity, said source having a starting bar device associated therewith;

cooling said axial wall structure of the mold for solidifying the molten metal therealong;'

heating the internal surface of said closed-end wall of the mold, to limit the subsequent solidification of the molten metal thereagainst during the casting operation, by the generation of heat external to the mold cavity prior to the casting operation; and relatively withdrawing the mold from the source of molten metal to form a solidified casting shell of said article with a molten core, molten metal from the source of molten metal flowing through the core of said article towards the closed-end wall structure of the mold during casting.

2. The process as defined in claim 1, wherein: said article is continuously cast of steel.

3. The process as defined in claim 1, wherein: said article is cast substantially horizontally.

4. The process asdefined in claim 1, further including the step of heating the internal surface of said closed-end wall of the mold during at least a portion of the casting operation by the generationof heat external to the mold cavity to limit solidification of the molten metal thereagainst.

5. Theprocess as defined in claim lsfurther including the step of oscillating at least the axial wall structure of the mold at least as early as the mold cavity is completely filled with metal from said source.

6. The :process as defined in claim 1 wherein the source of molten metal includes a container for such molten metal, and further including the step of abutting the outer face of side axial wall structure nearest said container with the container in an area surrounding that portion of the container from which molten metal exits from said container flowing toward said-mold.

7. The process as defined in claim 1, further including: the steps of cooling the periphery of. said end wall structure, and introducing into the mold cavity a lubricant under pressure between said cooled axial mold wall structure and said cooled portion of said closedend wall structure during the casting.

8. The process as defined in claim 1 further comprising: the steps of cooling the peripheral portion of said end wall structure, and introducing in said mold cavity a lubricant under pressure between a cooled peripheral portion of said end wall structure and said cooled axial wall structure of the mold, and oscillating said axial wall structure of the mold with reference to said end wall structure of the mold during casting to reduce adherence of the casting shell to said wall structure, and so as to distribute said lubricant as a thin film over a portion of the casting shellin proximity to said end wall structure.

9. The process as defined in claim 1 further including the steps of oscillating at least the axial mold wall structure of themold during the casting operation and beginning such oscillation at least as early as the mold cavity is completely filled with metal from said source, and moving said end wall axially within said axial wall structure to provide a mold with a variable effective mold cavity so as to enlarge the mold cavity during the commencement of the casting operation.

10. The process as defined in claim 1, further comprising the steps of moving said end wall axially within said axial wall structure to provide'a mold with a variable effective mold cavity, said moving of said end wall including movement of the latter to the end portion of said axial wall structure nearest said source, and preheating the face of said end wall nearest the source when said end wall is in the last-mentioned position thereof. 7

11. The process as defined in claim 1, further comprising the step of moving said end wall axially within sid axial wall structure to provide a mold with a variable effective mold cavity,-said moving of said end wall to vary the effective mold cavity including movement to the end portion of said axial wall structure nearest said source and moving said end wall to a position at the remote end portion. of said axial wall structure.

12. The process as defined in claim 1, further comprising the step of moving said end wall axially within said axial wall structure to provide a mold with a variable effective mold cavity, said moving of said end wall I to vary the effective mold cavity including movement to the end portion of said axial wall structure nearest said source and moving said end wall to a position at the remote end portion of said axial wall structure, said moving of said end wall to the end portion of said axial wall structure nearest said source being such that said end wall protrudes from the last-mentioned end portion, and preheating the face of said end wall nearest said source.

13. A process of continuously casting an elongated metal article, comprising the steps of:

introducing molten metal from a source of molten metal within a container into a mold having an axial wall structure and a closed-end wall structure, defining a mold cavity, said container having a starting bar device associated therewith;

cooling said axial wall structure of the mold for solidifying the molten metal therealong;

moving said closed-end wall of the mold from a relative forward position within said axial wall structure to a rear position therein during the filling of the mold cavity; and

relatively withdrawing the mold from said container,

at least as early as the reaching of said rear position of said end wall in said axial wall structure, to form a solidified casting shell of said article with a mo]- ten core, molten metalfrom the source of molten metal flowing through the core of said article toward said end wall of the mold during casting.

14. The process as defined in claim l3, further including the step of:

oscillating said axial wall structure during at least a portion of the casting operation.

15. The process as defined in claim 13, wherein said metal is steel.

16. The process as defined in claim 13, wherein said metal is iron.

17. The process as defined in claim casting is substantially horizontal.

18. The process as defined in claim 13, further comprising the steps of forming a lubricant around the circumference of the end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant being formed substantially at the axially forward end of said end wall and so that it may abut an in- 13, wherein the ternal surface portion of said axial wall structure; and

urging said lubricant in a direction to bring it against the last-mentioned internal wall surface to impinge thereon. 19. The process as defined in claim 13 further comprising the steps of:

forming a lubricant around the circumference ofthe end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant being formed substantially at the axially forward end of said end wall and so that it may abut an internal surface portion of said axial wall structure;

and

urging said lubricant in a direction to bring it against said internal wall structure surface to impinge thereon while, concurrently with the forming of said lubricant, forming in the same area-of the lastmentioned end wall, a seal to prevent metal in the mold cavity from passing said seal.

20.- The process as defined in claim 13 further comprising the steps of:

forming a lubricant around the circumference of the end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant being formed substantially at the axially forward end of said end wall and so that it may abut an internal surface portion of said axial wall structure; and

urging said lubricant in a direction to bring it against said internal wall structure surface to impinge thereon while, concurrently with the forming of said lubricant, forming in the same area of the last mentioned end wall, a seal to prevent metalin the mold cavity from passingsaid seal, said lubricant and said seal being formed from a common substance which is relatively rigid.

21. A process of continuously casting an elongated metal article longer than the mold, utilizing the technique of relatively separating a source of molten metal from a closed-end mold, comprising the steps of:

introducing molten metal from a source of molten metal within a container into a mold having an axial wall structure and a closed-end wall structure, defining a mold cavity, said container having a starting bar device associated therewith;

cooling said axial wall structure of the mold for solidifying the molten metal therealong;

moving said closed-end wall of the mold from a relative forward position within saidaxial wall structure to a rear position therein during the casting operation; and

preheating at least a portion of said end wall while in said forward position thereof and also said container prior to the reception in said container of said molten metal and prior to a casting operation, by generating heat within said container which heat impinges on the foward face of said end wall.

22. The process as defined in claim 21, wherein said end wall in said forward position thereof protrudes from said axial wall structure.

23. The process as defined in claim 21, further comprising the step of separately generating heat rearwardly of said face of said end wall to simultaneously heat from the rear a rear portion of said end wall.

24. The process as defined in claim 21, wherein: said wall face is spaced from said container.

25. The process as defined in claim 21, wherein said preheating is by generating hot gases which impinge upon the interior of said container and exit from said container to impinge upon said face of said end wall.

26. Apparatus for continuously casting an elongated metal article, comprising: a source of molten metal, a

- mold having a cooled axial wall structure and a closed end wall structure defining a mold cavity, a starting bar device associated with said source of metal, heating means external to the mold cavity to heat prior to a casting operation an internal surface portion of said mold end-wall structure to a temperature to limit solidification of the molten metal against said mold end wall structure, and means for relatively withdrawing said mold from said starting bar device in such a manner as to cause molten metal to flow through said starting bar device to said mold and form an article with a molten core flowing through a solidifying casting shell to said end wall structure, which shell forms on contact of the molten metal with said cooled axial wall structure of said mold.

27. Apparatus as defined in claim 26, wherein: the article is cast of steel and said source of metal and said mold are relatively moved apart along a substantially horizontal path during casting.

28. Apparatus as defined in claim 26, further including means for cooling a peripheral portion of said closed end wall structure, and further including means for introducing in said mold cavity between said cooled axial wall structure and said peripheral portion of said end wall structure a lubricant under pressure.

29. Apparatus as defined in claim 26, wherein said axial wall structure of said mold is supported for axial movement with reference to said end wall structure of the mold, and wherein there is further provided means for oscillating in an axial direction the axial wall structure of the mold with reference to said end wall structure of the mold during casting.

30. Apparatus as defined in claim 26, wherein said axial wall structure of the mold is supported for axial movement with reference to said end wall structure of the mold, said peripheral portion of said end wall structure being cooled, and wherein there is further provided means for introducing in said mold cavity from between said cooled axial wall structure and said peripheral portion of said end wall structure a lubricant under pressure, and means oscillating in an axial direction said axial wall structure of the mold with reference to said end wall structure of the mold during casting, reducing adherence of the casting shell to said axial wall structure and distributing said lubricant as a thin film over a portion of the casting shell in proximity to said end wall structure.

31. Apparatus as defined in claim 30 wherein: said means for introducing lubricant under pressure into the mold includes a pressure-relief valve in a lubricant supply conduit system, which valve opens on generation of excessive fluid pressure in the mold during a casting operation.

32. Apparatus for the continuous casting of a metal article comprising, in combination:

a source of molten metal,

a mold having a cooled axial wall structure and a closed-end wall structure, defining a mold cavity,

a starting bar device around a portion of which molten metalis introduced from said source of molten metal on introduction of molten metal into said mold cavity,

means moving said end wall of the mold from a relative forward position within said axial wall structure to a rear position therein during the filling of the mold cavity, and

means for relatively withdrawing the mold from said source, at least as early as the reaching of said rear position of said end wall in said axial wall structure, to form a solidified casting shell of said article with a molten core, molten metal from said source of molten metal flowing through said core of said article towards said end wall of the mold during casting.

33. Apparatus as defined in claim 32, further including oscillating said axial wall structure during at least a portion of the casting operation.

34. Apparatus as defined in claim 32, wherein the casting is substantially horizontal.

35. Apparatus as defined in claim 32 further comprising means forming a lubricant around thecircumference of said end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant being formed substantially at the axially forward extremity of said end wall and so that it may abut an internal surface portion of said axial wall structure; and means urging said lubricant forming means in a direction to bring it against said internal surface portion of said axial wall structure.

36. Apparatus as defined in claim 32, further including a container for said source of molten metal having a metal-receiving opening and a metal discharge opening, means to move at least said axial wall structure of the mold to abut said container around said discharge opening prior to a casting operation, and said starting bar device comprising finger-likeprojections extending outwardly from said container around said discharge opening and extensible into said mold cavity when said axial wall structure is abutted against said container.

37. Apparatus as defined in claim 35, wherein: said lubricant forming means comprises means forming a seal substantially at the axially forward end of said end wall and so that it abuts said internal surface portion'of said axial wall structure.

38. Apparatus as defined in claim 32, further including a container for said source of molten metal having a metal-receiving opening and a metal discharge opening, means to move at least said axial wall structure of the mold to abut said container around said discharge opening prior to a casting operation, and said starting bar device comprising finger-like projections extending outwardly from said container around said discharge opening and extensible into the mold cavity when said axial. wall structure is abutted against said container, said finger-like projections being formed on an element which is mounted on said container for detachment from said container subsequent to a casting operation.

39. Apparatus as defined in claim 32, further including a container for said source of molten metal having a metal-receiving opening and a metal discharge opening, means to move at least said axial wall structure of the mold to abut said container around said discharge opening prior to a casting operation, and said starting bar device comprising an element having openingdefining means which are undercut on the rearward face thereof to be in fluid flow communication with ence of said end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant forming means comprising a seal, said lubricant forming means being formed substantially at the axially forward extremity of said end wall and pressed against said internal surface portion of said axial wall structure. 

1. A process of continuously casting an elongated metal article, comprising the steps of: introducing molten metal from a source of molten metal into a mold having an axial wall structure and a closed-end wall structure, defining a mold cavity, said source having a starting bar device associated therewith; cooling said axial wall structure of the mold for solidifying the molten metal therealong; heating the internal surface of said closed-end wall of the mold, to limit the subsequent solidification of the molten metal thereagainst during the casting operation, by the generation of heat external to the mold cavity prior to the casting operation; and relatively withdrawing the mold from the source of molten metal to form a solidified casting shell of said article with a molten core, molten metal from the source of molten metal flowing through the core of said article towards the closed-end wall structure of the mold during casting.
 2. The process as defined in claim 1, wherein: said article is continuously cast of steel.
 3. The process as defined in claim 1, wherein: said article is cast substantially horizontally.
 4. The process as defined in claim 1, further including the step of heating the internal surface of said closed-end wall of the mold during at least a portion of the casting operation by the generation of heat external to the mold cavity to limit solidification of the molten metal thereagainst.
 5. The process as defined in claim 1 further including the step of oscillating at least the axial wall structure of the mold at least as early as the mold cavity is completely filled with metal from said source.
 6. The process as defined in claim 1 wherein the source of molten metal includes a container for such molten metal, and further including the step of abutting the outer face of side axial wall structure nearest said container with the container in an area surrounding that portion of the container from which molten metal exits from said container flowing toward said mold.
 7. The process as defined in claim 1, further including: the steps of cooling the periphery of said end wall structure, and introducing into the mold cavity a lubricant under pressure between said cooled axial mold wall structure and said cooled portion of said closed-end wall structure during the casting.
 8. The process as defined in claim 1 further comprising: the steps of cooling the peripheral portion of said end wall structure, and introducing in said mold cavity a lubricant under pressure between a cooled peripheral portion of said end wall structure and said cooled axial wall structure of the mold, and oscillating said axial wall structure of The mold with reference to said end wall structure of the mold during casting to reduce adherence of the casting shell to said wall structure, and so as to distribute said lubricant as a thin film over a portion of the casting shell in proximity to said end wall structure.
 9. The process as defined in claim 1 further including the steps of oscillating at least the axial mold wall structure of the mold during the casting operation and beginning such oscillation at least as early as the mold cavity is completely filled with metal from said source, and moving said end wall axially within said axial wall structure to provide a mold with a variable effective mold cavity so as to enlarge the mold cavity during the commencement of the casting operation.
 10. The process as defined in claim 1, further comprising the steps of moving said end wall axially within said axial wall structure to provide a mold with a variable effective mold cavity, said moving of said end wall including movement of the latter to the end portion of said axial wall structure nearest said source, and preheating the face of said end wall nearest the source when said end wall is in the last-mentioned position thereof.
 11. The process as defined in claim 1, further comprising the step of moving said end wall axially within sid axial wall structure to provide a mold with a variable effective mold cavity, said moving of said end wall to vary the effective mold cavity including movement to the end portion of said axial wall structure nearest said source and moving said end wall to a position at the remote end portion of said axial wall structure.
 12. The process as defined in claim 1, further comprising the step of moving said end wall axially within said axial wall structure to provide a mold with a variable effective mold cavity, said moving of said end wall to vary the effective mold cavity including movement to the end portion of said axial wall structure nearest said source and moving said end wall to a position at the remote end portion of said axial wall structure, said moving of said end wall to the end portion of said axial wall structure nearest said source being such that said end wall protrudes from the last-mentioned end portion, and preheating the face of said end wall nearest said source.
 13. A process of continuously casting an elongated metal article, comprising the steps of: introducing molten metal from a source of molten metal within a container into a mold having an axial wall structure and a closed-end wall structure, defining a mold cavity, said container having a starting bar device associated therewith; cooling said axial wall structure of the mold for solidifying the molten metal therealong; moving said closed-end wall of the mold from a relative forward position within said axial wall structure to a rear position therein during the filling of the mold cavity; and relatively withdrawing the mold from said container, at least as early as the reaching of said rear position of said end wall in said axial wall structure, to form a solidified casting shell of said article with a molten core, molten metal from the source of molten metal flowing through the core of said article toward said end wall of the mold during casting.
 14. The process as defined in claim 13, further including the step of: oscillating said axial wall structure during at least a portion of the casting operation.
 15. The process as defined in claim 13, wherein said metal is steel.
 16. The process as defined in claim 13, wherein said metal is iron.
 17. The process as defined in claim 13, wherein the casting is substantially horizontal.
 18. The process as defined in claim 13, further comprising the steps of forming a lubricant around the circumference of the end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant being formed substantially at the axially forward end of said end wall and so that it may abut an inTernal surface portion of said axial wall structure; and urging said lubricant in a direction to bring it against the last-mentioned internal wall surface to impinge thereon.
 19. The process as defined in claim 13 further comprising the steps of: forming a lubricant around the circumference of the end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant being formed substantially at the axially forward end of said end wall and so that it may abut an internal surface portion of said axial wall structure; and urging said lubricant in a direction to bring it against said internal wall structure surface to impinge thereon while, concurrently with the forming of said lubricant, forming in the same area of the last-mentioned end wall, a seal to prevent metal in the mold cavity from passing said seal.
 20. The process as defined in claim 13 further comprising the steps of: forming a lubricant around the circumference of the end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant being formed substantially at the axially forward end of said end wall and so that it may abut an internal surface portion of said axial wall structure; and urging said lubricant in a direction to bring it against said internal wall structure surface to impinge thereon while, concurrently with the forming of said lubricant, forming in the same area of the last-mentioned end wall, a seal to prevent metal in the mold cavity from passing said seal, said lubricant and said seal being formed from a common substance which is relatively rigid.
 21. A process of continuously casting an elongated metal article longer than the mold, utilizing the technique of relatively separating a source of molten metal from a closed-end mold, comprising the steps of: introducing molten metal from a source of molten metal within a container into a mold having an axial wall structure and a closed-end wall structure, defining a mold cavity, said container having a starting bar device associated therewith; cooling said axial wall structure of the mold for solidifying the molten metal therealong; moving said closed-end wall of the mold from a relative forward position within said axial wall structure to a rear position therein during the casting operation; and preheating at least a portion of said end wall while in said forward position thereof and also said container prior to the reception in said container of said molten metal and prior to a casting operation, by generating heat within said container which heat impinges on the foward face of said end wall.
 22. The process as defined in claim 21, wherein said end wall in said forward position thereof protrudes from said axial wall structure.
 23. The process as defined in claim 21, further comprising the step of separately generating heat rearwardly of said face of said end wall to simultaneously heat from the rear a rear portion of said end wall.
 24. The process as defined in claim 21, wherein: said wall face is spaced from said container.
 25. The process as defined in claim 21, wherein said preheating is by generating hot gases which impinge upon the interior of said container and exit from said container to impinge upon said face of said end wall.
 26. Apparatus for continuously casting an elongated metal article, comprising: a source of molten metal, a mold having a cooled axial wall structure and a closed end wall structure defining a mold cavity, a starting bar device associated with said source of metal, heating means external to the mold cavity to heat prior to a casting operation an internal surface portion of said mold end-wall structure to a temperature to limit solidification of the molten metal against said mold end wall structure, and means for relatively withdrawing said mold from said starting bar device in such a manner as to cause molten metal to flow through said starting bar device to said mold anD form an article with a molten core flowing through a solidifying casting shell to said end wall structure, which shell forms on contact of the molten metal with said cooled axial wall structure of said mold.
 27. Apparatus as defined in claim 26, wherein: the article is cast of steel and said source of metal and said mold are relatively moved apart along a substantially horizontal path during casting.
 28. Apparatus as defined in claim 26, further including means for cooling a peripheral portion of said closed end wall structure, and further including means for introducing in said mold cavity between said cooled axial wall structure and said peripheral portion of said end wall structure a lubricant under pressure.
 29. Apparatus as defined in claim 26, wherein said axial wall structure of said mold is supported for axial movement with reference to said end wall structure of the mold, and wherein there is further provided means for oscillating in an axial direction the axial wall structure of the mold with reference to said end wall structure of the mold during casting.
 30. Apparatus as defined in claim 26, wherein said axial wall structure of the mold is supported for axial movement with reference to said end wall structure of the mold, said peripheral portion of said end wall structure being cooled, and wherein there is further provided means for introducing in said mold cavity from between said cooled axial wall structure and said peripheral portion of said end wall structure a lubricant under pressure, and means oscillating in an axial direction said axial wall structure of the mold with reference to said end wall structure of the mold during casting, reducing adherence of the casting shell to said axial wall structure and distributing said lubricant as a thin film over a portion of the casting shell in proximity to said end wall structure.
 31. Apparatus as defined in claim 30 wherein: said means for introducing lubricant under pressure into the mold includes a pressure-relief valve in a lubricant supply conduit system, which valve opens on generation of excessive fluid pressure in the mold during a casting operation.
 32. Apparatus for the continuous casting of a metal article comprising, in combination: a source of molten metal, a mold having a cooled axial wall structure and a closed-end wall structure, defining a mold cavity, a starting bar device around a portion of which molten metal is introduced from said source of molten metal on introduction of molten metal into said mold cavity, means moving said end wall of the mold from a relative forward position within said axial wall structure to a rear position therein during the filling of the mold cavity, and means for relatively withdrawing the mold from said source, at least as early as the reaching of said rear position of said end wall in said axial wall structure, to form a solidified casting shell of said article with a molten core, molten metal from said source of molten metal flowing through said core of said article towards said end wall of the mold during casting.
 33. Apparatus as defined in claim 32, further including oscillating said axial wall structure during at least a portion of the casting operation.
 34. Apparatus as defined in claim 32, wherein the casting is substantially horizontal.
 35. Apparatus as defined in claim 32 further comprising means forming a lubricant around the circumference of said end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant being formed substantially at the axially forward extremity of said end wall and so that it may abut an internal surface portion of said axial wall structure; and means urging said lubricant forming means in a direction to bring it against said internal surface portion of said axial wall structure.
 36. Apparatus as defined in claim 32, further including a container for said source of molten metal having a metal-receiving opening and a metaL discharge opening, means to move at least said axial wall structure of the mold to abut said container around said discharge opening prior to a casting operation, and said starting bar device comprising finger-like projections extending outwardly from said container around said discharge opening and extensible into said mold cavity when said axial wall structure is abutted against said container.
 37. Apparatus as defined in claim 35, wherein: said lubricant forming means comprises means forming a seal substantially at the axially forward end of said end wall and so that it abuts said internal surface portion of said axial wall structure.
 38. Apparatus as defined in claim 32, further including a container for said source of molten metal having a metal-receiving opening and a metal discharge opening, means to move at least said axial wall structure of the mold to abut said container around said discharge opening prior to a casting operation, and said starting bar device comprising finger-like projections extending outwardly from said container around said discharge opening and extensible into the mold cavity when said axial wall structure is abutted against said container, said finger-like projections being formed on an element which is mounted on said container for detachment from said container subsequent to a casting operation.
 39. Apparatus as defined in claim 32, further including a container for said source of molten metal having a metal-receiving opening and a metal discharge opening, means to move at least said axial wall structure of the mold to abut said container around said discharge opening prior to a casting operation, and said starting bar device comprising an element having opening-defining means which are undercut on the rearward face thereof to be in fluid flow communication with said mold cavity when said axial wall structure is abutted against said container.
 40. Apparatus as defined in claim 39, wherein: said element having opening-defining means is detachably secured to said container for removal subsequent to a casting operation.
 41. Appratus as defined in claim 32, further comprising: means forming a lubricant around the circumference of said end wall in a manner such that the lubricant is axially movable with said end wall, said lubricant forming means comprising a seal, said lubricant forming means being formed substantially at the axially forward extremity of said end wall and pressed against said internal surface portion of said axial wall structure. 